Work has continued on determining if (1) there is an age-dependent loss at the cellular level of proper gene regulation and (2) whether there is a correlation between a mammalian species' innate and longevity or aging rate and the intrinsic ability of cells to maintain their proper state of differentiation. Studies on the age-dependent expression of murine leukemia virus in thymus, brain and liver of AKR mice have been completed. Results indicate that even non-target tissues of leukemia virus, such as liver, show an age-dependent increase in the amount of leukemia-like RNA in the nuclei. We have also found a good correlation between a mammalian species' innate aging rate and its age-dependent onset frequency of various types of cancer. Such data suggests that cells of longer-lived species may have a life-long higher stability against genetic modifications leading to cancer. Thus, cancer and aging may have both commin causes and rate-governing processes.